AbstractIn this paper we consider the problem of designing a controller for an uncertain linear time‐invariant (LTI) system; the control objective is that of asymptotic error regulation for reference and disturbance signals which are described by a known unforced differential equation. In particular, we are concerned with the case in which this differential equation describes linear combinations of sinusoidal and constant functions; we show that under mild (almost necessary) structural requirements on the plant, prior knowledge of the order of an LTI exponentially stabilizing compensator is sufficient to achieve this control objectiv